SHACL/ShEX constraint to make a property to build a hierarchy (i.e. a tree)

Question

I have very little knowledge of SHACL and ShEx.

I've been reading about them and to figure out whether I could create constraints over a property to make it define a hierarchy (i.e. a tree-like structure).

I guess what I'm looking for is a way to specify that, for a given property p,

a) this can happen (o1 != o2):

   s p o1 .
   s p o2 .
   ...
   s p oN

b) but this cannot (s1 != s2):

   s1 p o .
   s2 p o

I guess for a) I should use some kind of constraint on the cardinality of p, right?

No idea on how to specify b) or even if it is possible at all using either SHACL or ShEX. Should I be using OWL?

Answer 1

In OWL

Assuming DifferentIndividuals: :s1, :s2 etc.:

ObjectProperty: :p
  Characteristics: InverseFunctional

In ShEx

With shape map like {_ :p FOCUS} @ :Shape:

:Shape { 
  ^:p IRI ?
}

Example

In SHACL

:Shape a sh:NodeShape ;
  sh:targetObjectsOf :p ;
  sh:property [
    sh:path [ sh:inversePath :p ] ;
    sh:maxCount 1 
  ] .

Example

In pure SPARQL

ASK { ?o ^:p ?s1, ?s2 . FILTER (?s1 != ?s2) }

In general

Read "Validating RDF Data".